How to store research peptides long term at -20 C
Why -20 C for lyophilised powder, the frost-free freezer problem, how to organise storage, and what to do with a vial stored longer than intended.
The single most effective thing a laboratory can do to protect a research peptide costs nothing: keep the sealed vial at -20 C in the dark until the day it is needed. This note covers long-term storage of lyophilised peptides, the difference -20 C and -80 C make, how to organise a freezer so vials are not lost or repeatedly warmed, and what to do when a vial has been stored longer than intended. All Alphex products are for laboratory and in-vitro research only.
Why -20 C for powder
Lyophilised peptide degrades slowly at room temperature and very slowly at -20 C. The residual moisture in the cake is immobilised, oxidation from trapped air is negligible in the dark, and the peptide is not moving. For the compounds in the Alphex catalogue, sealed vials at -20 C are stable for years; at 2-8 C for months; at 20-25 C for weeks with no measurable change, which is why ambient shipping is fine.
The recommendation is -20 C rather than a colder freezer for practical reasons: a domestic or laboratory -20 C is universally available, the additional benefit of -80 C for freeze-dried short peptides is marginal, and frost-free freezers that cycle above 0 C to defrost are the thing to avoid at either temperature.
Frost-free freezers
Domestic frost-free freezers periodically warm their coils to shed ice; the chamber can rise several degrees during each cycle. Over months that is hundreds of small temperature swings. Peptide powder tolerates it better than solutions do, but a laboratory freezer without auto-defrost, or a well-insulated box inside a frost-free unit, is better. Never store vials in the door.
Organising storage
- Keep vials sealed until use. Do not open a vial "to check it".
- Dark. A closed box. GHK-Cu is light sensitive; the others tolerate light better but there is no reason to expose them.
- Dry. Put vials in a sealed container with a desiccant sachet if the freezer is humid or opened often. Condensation on the outside of a vial is harmless; moisture inside is not, and it gets inside only through a compromised seal or an opened vial.
- Log it. Compound, batch number, receipt date, location. Alphex batch numbers on the label match the COA; recording them means any later question about a result can be traced to a certificate.
- Warm before opening. 15-20 minutes at room temperature, still sealed. See reconstitution.
Reconstituted stock in the freezer
Solutions can be frozen at -20 C as single-use aliquots and last months when thawed once. Repeated freeze-thaw is what shortens their life. The routine is in can you freeze reconstituted peptides and aliquoting peptide stock solutions.
Vials stored longer than intended
A sealed vial found at the back of a -20 C freezer after two years is very likely fine. Check the seal (stopper domed inward, air rush on puncture) and the appearance (cake or film present, no discolouration). If both are normal, reconstitute and, for a critical assay, verify against a fresh vial or by HPLC before relying on it. If the vial has been at room temperature for months, or the seal is gone, treat it as suspect. Alphex can tell you the original test date for any batch number.
Frequently asked questions
Is 2-8 C good enough?
For weeks to a few months, yes. For longer, -20 C.
Does -80 C help?
Slightly, for very long storage or unusually sensitive peptides. For the catalogue compounds -20 C is sufficient.
Can I store different peptides in the same box?
Yes, sealed vials do not interact. Label the box and keep a list.
Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 30 March 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.